﻿using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.Drawing;          //重要引用
using System.Drawing.Imaging;    //重要引用
using System.IO;                     //重要引用
namespace UI.Admin.Login
{
    public partial class ValidateCode : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            //生成4位的验证码
            string tmp = RndNum(4);
            Session["validate_code"] = tmp;
            HttpCookie a = new HttpCookie("ImageV", tmp);
            Response.Cookies.Add(a);
            this.ValidateCodemain(tmp);
        }
        private void ValidateCodemain(string VNum)
        {
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            int gheight = VNum.Length * 20;
            Img = new Bitmap(gheight, 30);
            g = Graphics.FromImage(Img);
            //背景颜色
            g.Clear(Color.White);
            //文字字体
            Font f = new Font("Arial Black", 13);
            //文字颜色
            SolidBrush s = new SolidBrush(Color.Black);
            g.DrawString(VNum, f, s, 15, 1);
            ms = new MemoryStream();
            Img.Save(ms, ImageFormat.Jpeg);
            Response.ClearContent();
            Response.ContentType = "image/Jpeg";
            Response.BinaryWrite(ms.ToArray());

            g.Dispose();
            Img.Dispose();
            Response.End();
        }

        private string RndNum(int VcodeNum)
        {
            string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p" +
             ",q,r,s,t,u,v,w,x,y,z";
            string[] VcArray = Vchar.Split(new Char[] { ',' });
            string VNum = "";
            int temp = -1;

            Random rand = new Random();

            for (int i = 1; i < VcodeNum + 1; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
                }

                int t = rand.Next(35);
                if (temp != -1 && temp == t)
                {
                    return RndNum(VcodeNum);
                }
                temp = t;
                VNum += VcArray[t];
            }
            return VNum;
        }
    }
}